how to Allow users to comment on Blogger using Google+

Blogger’s integration with Google+ can help you to spread the word about
your blog, engage your readers in discussion, and share your content to a
wider audience. Depending on when you signup for Blogger, you might have  the option in associating your Google+ profile with your blog during  sign-up process. If not, or you didn’t create the association at the time, you can easily return to the settings area later and connect the two services. Once connected, you can choose to associate certain blogs with a Page, or certain blogs with your profile on Google+. This allows you to automatically share posts to your streams once they’re published, providing automatic promotion of your content! If you blog under your common name (such as ‘Joe Bloggs’s blog’), you may find that the association between Google+ and your blog will increase the discoverability of your blog – as the link works both ways, search
results that lead to your Google+ profile will also allow users to find your blog. You’re also
able to directly share posts from Blogger to your personal stream once the two are connected, making it easier to be sociable!

1. Create your blog: If you don’t have a Blogger blog, you’ll need to create one to be able to connect your Google+ account to. Visit www.blogger.com and sign in to manage your existing blog 
2. Blogger welcome: Once signed in, you can manage all your Blogger blogs. Once you have created a blog, click on the gear icon and select ‘Connect to Google+’ from the pop-up menu.
3. Settings panel: The Settings panel will open on the Google+ tab. Take a quick look at the other options in this area. We’ve got a comments tab, but this will disappear once we’ve set up Google+ for comments.
4. Add blogs: Back in the Google+ setup wizard, you’ll see a list of your blogs; tick each checkbox to enable the link between your Blogger blog and Google+. Select the blog(s) you’d like to link and click Add Blogs.
5. Updates to Blogger: If you already have a Blogger profile, you’re warned that by linking your two accounts you’ll replace your Blogger profile with the information from Google+. A handy preview shows you what this will look like.
6. Accept the terms: Tick the checkbox at the bottom of the preview screen and click the Switch Now button to confirm your accounts-linking request. If you change your mind later, you can revert to separate accounts.
7. Confirmation screen: You’ll be returned to the Settings area, showing the Google+ settings. Two checkboxes beneath your profile let you choose if you should be prompted to share after posting and use Google+ for comments.
8. Use Google+ comments: Tick the checkbox for Google+ comments and all comments on your blog will use the Google+ account, allowing other people to see when visitors comment on your blog from their Google+ page.
9. Your Google+ page: If you now go to your own Google+ page you’ll notice that your blog appears in your profile. You can control which circles can see this information, allowing you to restrict access as desired.